There are two types of adjectives in Japanese: い-adjectives and な-adjectives. い-adjectives all end with ～い (ex: たのしい) while な-adjectives end with ～な, even though they end with ～な (ex:すき[な]). The ～な is often times excluded from the words that fall under this category because it isn't used most of the time. い-adjectives and な-adjectives conjugate differently:たのしい -- Funすき(な) -- Like

Along with い-adjectives and な-adjectives, there is also one that is irregular. This adjective is いい (good). The ending of いい follows the same pattern as い-adjectives, but in most cases the first い changes to a よ. While いい is the only irregular adjective, there are other adjectives that end with いい, like かっこいい. Here is a chart of how to conjugate irregular adjectives:

Affirmative

Negative

present

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いいです

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よくないです

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or (よくありません)

Past

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よかったです

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よくなかったです

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or (よくありませんでした)

These chart show how to use the adjectives when you are explaining a subject. Here is an example:こん本はむずかしいです。 "This book is difficult."むずかしい -- Difficult

When using an adjective along with some type of action, you put the adjective before the subject. Here are two examples:おもしろいえいがをみませんでした。 "I didn't see an interesting movie."きれいなへやにいきます。 "I will go to the clean room."おもしろい -- Interesting / Amusing / Funnyきれい(な) -- Clean / Beautifulへや -- Room